156 AVES. 



The bony tail is very short, [and consists in most instances of nine vertebr?e, the 

 three last of which are commonly anchylosed into a plough-share form, and are gene- 

 rally collectively styled the coccyx], but has a range of strong feathers, which, when 

 spread out, assist in supporting the bird : their number is ordinarily twelve ; sometimes 

 fourteen, and in many of the Gallinacea eighteen ; [in some few genera, as the 

 Grebes, Nandou, &c., these are wanting altogether ; a single Humming-bird {Trochilus 

 enicurus) possesses only six ; the Ani eight ; the rest of the Humming-birds, and 

 various others, ten ; while the Swans present from eighteen to twenty-two. The two 

 central of these feathers are implanted above the even line formed by the insertion of 

 the rest, and essentially correspond to the wing-tertiaries, as the others do to the 

 wing-secondaries ; the latter being in no instance moulted more than once in the year, 

 the former in many instances twice : we might accordingly designate the two central 

 tail feathers, which differ conspicuously from the rest in structure, uropygials. Above 

 and below the tail are lengthened feathers, commonly of weak texture, known as the 

 vpper and under tail-coverts. 



The rest of the feathers of Birds are named from their position, a.sfro?ital, coronal, 

 occipital, nuchal, dorsal or interscapular]/, which together form a continuous series, apart 

 from the scapalaries ; those in front of the eye are termed loral,a.nd the auditory aperture 

 is covered by a range styled auriculars, or ear- coverts : the sides of the neck and medial 

 portion of the sternal and abdominal region are at most covered with down ; the 

 former being concealed by the lateral feathers of the fore and hind neck meeting ; the 

 latter by a similar junction of two distinct lateral ranges. As it is necessary that the 

 warm body of a bird should be in actual contact with the eggs during incubation, 

 whatever down may cover the medial inferior region disappears in the females towards 

 the season of propagation, even in those confined in cages, so that this bareness is not 

 produced mechanically. Finally, besides various accessory tufts in different genera, 

 some long slender feathers are situate at the base of the wing internally, which are 

 named axillaries]. 



The legs have a femur, a tibia, and a peronpeum attached to the femur with a spring, 

 which maintains their extension without effort on the part of the muscles. The tarsus 

 and metatarsus are represented by a single bone, terminating below in three pullies. 



Most commonly there are three toes before, and a thumb behind* ; the latter being 

 sometimes deficient. In the Swifts it is directed forwards, [though half-reversible : in 

 the Moth-hunters and some others, inward, at a right angle with the axis of the body]. 

 In the yoke-footed Birds, on the contrary, the external toe and the thumb are dis- 

 posed backwards [most usually, but sometimes (as in the Touracos and Puft'-birds) 

 laterally : in the Trogons, the first and second toes are opposed to the third and 

 fourth ; and accordingly the longest toe, or that which corresponds to the middle one 

 in the generality of the class, is inward, instead of being oiitivard, as in all the other 

 yoke-footed groups]. The number of articulations increases in each toe, commencing 

 with the thumb, which has two, and ending with the external toe, which has five. 

 [The Swifts present a remarkable exception ; and it may be remarked that, in the 

 Ostrich alone, only two toes are present.] 



In genera', [invariably]. Birds are covered with feathers, a sort of tegument best 



♦ The word </i«m6 is here ami subsequently usi'd merely in a iiopular 1 thumbs of the Quadriimaua arc represented, in the class of Biids, 

 sense, to signify its antajjonism to the other digits: as the hinder 1 only by the tarsal spurs of many 6'(./.'inucfil.— Ko. 



